Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Taxes [Abstract]
Effective income tax rate (in hundredths)	40.40%	44.30%
U.S. Federal statutory rate (in hundredths)	35.00%
Expected annual effective income tax rate	approximately 36% to 38%
Gross unrecognized tax benefits, including interest and penalties	$ 32.8		$ 32.3
Related tax benefits	(1.9)		(1.9)
Net unrecognized tax benefits	$ 30.9		$ 30.4